Known from the publication DE 103 05 241 A1 is a 6-speed or 7-speed dual clutch transmission. The dual clutch transmission comprises two clutches, each connected with their inputs to the drive shaft and the output to one of the two transmission input shafts. The two transmission input shafts are coaxially positioned towards each other. In addition, two countershafts are axially parallel to the transmission input shafts, their idler gear wheels mesh with the fixed gear wheels of the transmission input shafts. Furthermore, coupling devices that are axial movable are connected in a rotationally fixed manner to the countershaft to shift the respective gear wheels. Each selected ratio is transferred by the drive gear wheels to a differential transmission. To achieve the desired gear ratio steps in this known dual clutch transmission, a large number of wheel planes are required, so that a significant amount of installation space is required.
In addition, a spur gear variable-speed transmission is known from the publication DE 38 22 330 A1. The spur gear variable-speed transmission comprises a dual clutch that can be shifted under load one part of which is connected to a drive shaft and the other part is connected to a hollow drive shaft, rotatably supported on the drive shaft. For certain gear ratios, the drive shaft can be coupled with the hollow drive shaft through a shifting device.
Known from the publication DE 10 2004 001 961 A1 is a shift-under-load transmission with two clutches, each of which are assigned to a partial transmission. The transmission input shafts of the two partial transmissions are positioned coaxially with respect to each other and mesh, via fixed gear wheels, with idler gear wheels of the designated countershaft. The respective idler gear wheels of the countershafts can be connected in a rotationally fixed manner to the respective countershaft by means of designated shifting devices. The particular idler gear wheels of the countershaft can be connected in a rotationally fixed manner by means of the assigned shifting devices with the associated countershaft. A 7-gear transmission, among other things, is known from this publication in which an additional shift element is provided to connect the two transmissions input shafts to establish an additional transmission stage. The 7-gear transmission requires in this embodiment at least six wheel planes in the two partial transmissions, to achieve the transmission stages. This increases the construction length of the transmission in the axial direction, thereby significantly limiting its use in a motor vehicle.